The SON gene is located on the long arm of chromosome 22. SON is important for recognizing sites in the human DNA that need ‘cutting and pasting’ by a specific machinery to generate functional proteins. Importantly, some of the proteins SON recruits for cutting and pasting by this machinery are important in the development of the brain and the nervous system. Hence, some of the clinical symptoms observed in individuals with SON mutations, are in fact the result of ‘cut and paste’ errors of the proteins regulated by SON.
Disease-causing mutations in the SON gene lead to half the amount of normal SON protein. As this level is insufficient to recruit the machinery to all sites in the human genome where needed, it cannot properly execute its regulatory function towards other genes.
Disease-causing mutations in SON often occur ‘de novo,’ this means the mutation is present for the first time in one family member as a result of a mutation in a germ cell (egg or sperm) of one of the parents or in the fertilized egg itself. The inheritance mode is therefore ‘autosomal dominant’, which means that there is a 50% chance to pass this mutation to offspring, should individuals with SON mutations have children themselves.